Electrical slip ring and support



Dec. 19, 1961 J. M. SCHELLER 3,014,193

ELECTRICAL SLIP RING AND SUPPORT Filed June 26, 1958 H INVENTOR. w-r'i ixg JULIUS M. SCHILLER A TORNEY United States Patent 3,014,193 ELECTR CAL SL P AND SUPPORT Julius M. Schiller, Hasbrouck Heights, N.J., assignor to 'Electro Tec C0rp.,-:South Hackensack, N.J., a corporation of New Jersey Filed June "26, 1958, Ser. No. 7 44,785 1Claini. (61; 339-8) It has beencommon practice in making slip ring as- .semblies and other structures including electrical contact or slip layeraspecifically'slip rings, to apply the contac layer orslip layer to a dielectric base such as a cylinder or a plate, for example, by an electrodeposition process. This practice leaves much to be desired, particularly in that the dielectric base members are too .weak to withstand strains incident to use and they tend to warp; they are not capable of carrying high electrical voltages and they easily become overheated so that the dielectric ring is weakened and the slip layer or the brush co-acting therewith may be damaged by overheating. Also, the heating of the slip layer sets up a thermal shock that tends to pull apart or separate" the slip layer and the base member.

A primary object of the present invention is to provide a novel and improved'constr'uction and combination of an electrical conducting slip layer and a base therefor in insulated relation' thereto, and a method of making it, whereby the combination will'be structurally and mechanically strong, will possess high current-carrying capacity and will be capable of withstanding high temperatures and of rapid cooling.

Another object isto provide a novel and improved construction and combination of a metallic base member, such as an aluminum cylinder .or plate, a slip or contact layer of electrical conducting material such as silver or a silver alloy, and a layer of insulating material or dielectric, wherein the metal base Will provide a structurally strong support for the slip layer, the differential of coefiicients of thermal expansion between the parts will be small, and the dielectric layer will be thin so that the heat may quickly pass from the slip layer through the dielectric layer to the metallic base, thereby to reduce thermal shock such as would induce pulling apart of said layers and the base.

Further objects of the invention are to provide a novel and improved method of making such a combination of a metal base, a slip layer, and a layer insulation, which will be simple and relatively inexpensive and by which a reliable, durable, and inexpensive structure can be produced; and to provide in such a method a novel and improved manner of connecting a lead wire or terminal mechanically to the base and electrically and mechanically to the slip layer.

Other objects of the invention will be brought out by the following description .in conjunction with the accompartying drawing in which FIGURE 1 is an end elevation of a slip ring assembly constructed in accordance with the invention;

FIGURE 2 is a partial side elevation and partial central vertical longitudinal sectional view on the plane of the line 2-2 of FIGURE 1;

FIGURE 3 is a fragmentary enlarged vertical longitudinal sectional view on the plane of the line 3-3 on FIGURE 2.;

FIGURE 3A is a fragmentary plane view of a portion of the construction shown in FIGURE 3;

FIGURE 4 is a fragmentary vertical longitudinal sectional view of a portion of the metal base cylinder showing the first step in the method of making the slip ring assembly;

FIGURE 5 is a similar view showing the next step of the method;

3,014,193 Patented Dec. 19, 1961 FIGURE 6 is a view similar to FIGURE 5 showing the next'following step of the method;

FIGURE7 is a similar view showing the next subsequent step of the method; and

FIGURE 8 is a greatly enlarged fragmentary vertical sectional view showing portions of a slip layer, the'base, the dielectric layer, and .a'lead wire of the finished slip ring assembly.

For the purpose of illustrating the principles of the invention, I have shown the invention as embodied in a generally known type of slip ring assembly, but it should be understood that the invention is susceptible to use in the construction of other slip ring or commutator assemblies and the like.

Specifically describing the invention, the base member A is shown in the form of a cylindrical tube or sleeve composed of a suitable metal such as aluminum, and adapted to be fitted on a shaft which supports the slip ring assembly in the desired relation to a co-acting brush or other element. The base member has a plurality of grooves 1 in its inner periphery, one to provide a clearance between the supporting shaft and the base member .bored through the base member at the bottom of .each of the grooves 5 to provide for the attachment of a lead wire 2 or other terminal element or stud. The holes 6 are made larger in diameter thanthe wire or terminal.

Thereupon, a layer of a suitable dielectric material such as an epoxy resin is applied or overcast and bonded on the surfaces of grooves 5 and the outer surface of the base member including the lands 7, as shown in FIG- URE 5.

The dielectric layer is then machined to form a groove 8 for each slip ring so as to leave a layer of the dielectric material on all surfaces of the grooves, on the lands or barriers 7, and within the holes 6 as shown in FIGURE 6. The thickness of the dielectric layer will vary accord ing to the nature of the material and the degree of insulation required, but the layer is formed of such material and of such thickness as to satisfy the dielectric requirements; and the plastic to metal ratio is extremely low so that exceptionally small slip ring assembly having the required electrical and mechanical characteristics can be produced. The dielectric material and the metals are such that the coefficient of thermalexpansion difiertial is exceptionally small. A hole 9 is formed in the dielectric layer in register with each of the holes 6 in the metal base member, and the lead wire or terminal element is then secured as by cement in said hole with the conducting portion of the wire or terminal element exposed at the bottom of the corresponding groove 8, as thus shown in FIGURES 7 and 8. For the purpose of illustration, the lead Wire 2 has been shown in FIGURE 8 as comprising the usual conducting core or wire 10 encased in the usual sheath 11 of insulating material.

Thereupon, the slip layers 3 are electrolytically bonded directly to said conducting portion 10 of the lead wire. The method of electrodepositing the slip layers is a secondary consideration, and any suitable electrodeposition method may be utilized, for example, the method described in Patent No. 2,696,570 dated December 7, 1954. If desired, the whole outer surface of the dielectric layer may be preliminarily coated with a conducting powder suspended in lacquer, and then the Whole outer surface may have a silver alloy electrodeposited on said coating to a sufficient thickness to fill the grooves S and extend beyond the side walls of the grooves as shown in FIG- URE 7; or the electrodeposit may be limited to only the grooves by applying the conducting coating to only the surfaces of the grooves. In either case, the coating will be omitted or removed from the exposed ends of the lead wires before the electrodepositing operation is performed.

After the electrodeposition has been completed, the outer surface of the assembly is machined, for example, in a lathe, to remove the surplus electrodeposited ma terial, finish the outer or slip surfaces of the slip layers 3 and leave the slip layers insulated from the base member and the outer surface of the base member, except the slip surfaces, coated and insulated by the dielectric layer 4 as shown in FIGURES 3 and 8.

With this method and construction, it will be seen that the metal base A provides a strong support for the slip layers, the dielectric layer is exceptionally thin and the coefficients of thermal expansion of the metals are so similar and the dielectric layer is so thin that heat may quickly pass from the slip layers through the dielectric layer to the base metal and thereby reduce the possibility of overheating of the slip layer or the dielectric layer and also reduce the possibility of such thermal shock as might tend to pull the slip layers and dielectric layer away from the metal base. The use of such a thin dielectric layer makes possible the construction of exceptionally small, and at the same time, strong and durable slip ring assemblies.

It will be understood by those skilled in the art that instead of aluminum, other metals may be utilized in forming the base members, and instead of epoxy resins, it is possible to use other suitable dielectrics such as polyurethane, silicones, and polyethylene.

While the invention has been shown and described in connection with a specific type of slip ring assembly,

it will be understood that this is primarily for the pur- 4- pose of illustrating the principles of the invention of the now prepared embodiment thereof, and that the invention may be used in the construction of other shapes and types of metal base members and slip layers within the spirit and scope of the invention.

What I claim is:

A slip ring assembly comprising a rigid metal base member having a groove in a surface thereof, a thin layer of dielectric material bonded to the side walls and bottom of said groove and to said surface of the base member at opposite sides of said groove to insulate said surface, and a slip ring comprising a layer of electrically conductive material electrolytically deposited on said layer of dielectric material in said groove, the plastic to metal ratio of the dielectric layer, the base member, and said slip ring being small and the differential of the coefiicients of thermal expansion of said base member, said dielectric layer and said slip ring being low providing for rapid transmission and dissipation of heat from the slip ring through the dielectric layer to the metal base member and thereby reducing thermal shock tending t pull the slip ring and the dielectric layer away from the metal base member.

References Cited in the file of this patent UNITED STATES PATENTS 1,176,632 Werner Mar. 21, 1916 1,431,295 Evans Oct. 10, 1922 1,711,858 Samminiatelli May 7, 1929 1,731,892 Ferris Oct. 15, 1929 1,906,691 Lilienfeld May 2, 1933 2,414,957 Larrabure S. Jan. 28, 1947 2,436,949 Anderson Mar. 2, 1948 2,641,050 Graybill et al. June 9, 1953 2,653,376 Fletcher et al. Sept. 29, 1953 2,696,570 Pandapas Dec. 7, 1954 OTHER REFERENCES Allen et al.: Electrical Manufacturing, May 1956, pages 

